• 구강회복응용과학지
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• 제21권2호
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• pp.153-167
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• 2005

The purpose of this study was to compare the v-shape thread with the square shape thread of fixture in the view of stress distribution pattern using finite element stress analysis. The finite element model was designed with the parallel placement of two standard fixtures(4.0 mm diameter ${\times}$ 11.5 mm length) on the region of mandibular 1st and 2nd molars. Three dimensional finite element model was created with the components of the implant and surrounding bone. This study simulated loads of 200 N at the central fossa in a axial direction (load A), 200 N at the buccal offset load that is 2 mm apart from central fossa in a axial direction (load B), 200 N at the buccal offset load that was 4 mm apart from central fossa in a axial direction (load C). These forces of load A',B',C' were applied to a $15^{\circ}$ inward oblique direction at that same site with 200 N. Von Mises stress values were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study : 1. The highest stress concentration occurred at the cervical region of the implant fixture. 2. Von Mises stress value of off-site region was higher than that of central fossa region. 3. Square shape thread type showed more even stress distribution in the vertical and oblique force than V-shape thread type. 4. Stress distribution was the most effective in the case of buccal offset load (2, 4 mm distance from central fossa) in the square shape thread type. 5. V-shape thread type revealed higher von Mises stress value than square shape thread type in all environmental condition. The results from numerical analyses concluded that square shape thread type had the lower destructive stress and more stress distribution between the fixture and bone interface than V-shape thread type. Therefore, square shape thread type was regarded as optimal thread configuration in biomechanical concepts.

• 대한토목학회논문집
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• 제31권3A호
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• pp.189-198
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• 2011

각국 강구조물 시공현장에서 사용되고 있는 고장력볼트의 인장강도는 1,000 MPa급이 주종을 이루고 있으나, 고강도강과 극후판의 개발과 강교량 건설기술의 발전에 따른 교량 지간의 장대화로 인하여 강도가 큰 새로운 볼트 개발이 요구되고 있다. 현재, 인장강도 1,300 MPa급의 고장력볼트가 개발되어 사용중에 있다. 그러나 고장력볼트는 작은 단면에 큰 하중이 작용하기 때문에 고강도볼트에서는 응력집중이 완화된 나사형상과 구조성능이 우수한 고장력볼트가 보다 효과적이다. 본 연구에서는 KS에서 규정된 나사형상보다도 우수한 나사형상을 개발하기 위하여 해석적 연구를 수행하였다. 나사형상에 대한 특성을 분석하여 볼트와 너트 체결시에도 하중분배가 효과적이고 응력집중이 완화된 신나사형상을 제안하였다. 또한, 실험적 연구에서는 인장강도 1,300 MPa급의 고장력볼트를 대상으로 구조성능에 대해서 실험연구를 수행하였다. 연구결과 신나사형상이 기존의 나사형상보다도 응력집중 완화효과와 구조성능효과가 있음이 검증되었다.

• 소성∙가공
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• 제19권3호
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• pp.160-166
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• 2010

In this paper, the process parameters of thread rolling were designed based on the numerical analysis results. Firstly, the effective analysis conditions that guarantee the reliability of the analysis results were found. To find the effective analysis conditions, the analyses were carried out for various numbers of teeth. And then, the effects of the process parameters such as tool shape and temperature on the thread rolling performance were investigated. The formability in thread rolling process was evaluated in terms of Cockcroft-Latham damage value. In order to evaluate formability, Cockcroft-Latham damage value was normalized by the critical damage value which was obtained from the analysis of uniaxial tensile test. The analyses were carried out using DEFORM-3D. The results showed that the flank angle and crest round had an effect on the thread rolling load. It was also shown that temperature had significant effects on the effective strain distribution, rolling load, and damage. With the reduced formability of stainless steel at higher temperature, it was shown that the normalized damage values increased as the process temperature.

• 대한한의학회지
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• 제34권3호
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• pp.1-12
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• 2013

Objectives: This was study about identifying fine seed herbs that are highly mixed together: Celosiae Semen, Celoisae Cristatae Semen, Cuscutae Semen, Perillae Semen. Methods: In non-distinctive herbs through sensory test, we can find accurate discriminative points by using a stereoscope. As a result, a new discriminative key was completed. Results: We identified a comparison of herbs which are mixed up in distribution. 1) In the case of Celosiae Semen and Celoisae Cristatae Semen, Celoisae Cristatae Semen which is mixed up is bigger and more glossy and especially have the sunk umbilicus. 2) In the case of Cuscutae Semen and Perillae Semen, Perillae Semen is discriminated by characteristic morado netting surface and impression of fruit stalk in the single-ended. 3) In the case of Cuscutae Semen which is distributed in three species, we discriminated by beak shape, location of umbilicus and vomiting thread shape or not when put in water. (1) Cuscuta chinensis has a weak beaky shape, an umbilicus in center and is vomiting thread shape when put in water. (2) C. australis has very weak beaky shape, an umbilicus beneath and is vomiting thread shape when put in water. (3) C. japonica has clear beaky shape, an umbilicus beneath and is not vomiting thread shape when put in water. Conclusions: A stereoscope can be effectively used for identifying fine seed herbs hardly distinguishable by sensory tests.

• 복식
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• 제65권2호
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• pp.92-104
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• 2015

Colored thread quilting is sewed up padded with Han-Ji (한지, korean paper) string using colored thread. This showed up geometric pattern with repeated line of straight, diagonal, curve. According to geometric pattern, Colored thread quilting showed visual effects. The purpose of this study is to present manufacturing techniques, kinds, use, shape of traditional colored thread quilting. furthermore, This study has produced fashion items that can be used in modern life by using techniques of colored thread quilting. According to the fashion items, It present succession and utilization of techniques of colored thread quilting. This study was conducted in the following manner First, It studied traditional colored thread quilting techniques through the documents consideration, previous researches and by surveying antiquity in the museum. 2nd, It tried to make a reproduction about techniques of traditional colored thread quilting. 3rd, This study has selected and developed item and design of fashion items that can be used pragmatically in modern life by using techniques of colored thread quilting. And Fashion items that have been produced in this study is a total 10 kinds that was composed of Vest 4ea, Pendant & Brooch 6ea. Colored thread quilting is a unique technique of thread quilting that combines powerful practicality with decorativeness only in korea. These technique hope that it can developed more variety of items in modern life.

• 대한치과보철학회지
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• 제52권4호
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• pp.279-286
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• 2014

목적: 임플란트가 식립되는 동적과정을 유한요소해석으로 모사하여, 임플란트 나사형상 차이가 변연골의 식립 응력발생에 미치는 영향을 조사하고자 한다. 재료 및 방법: 코어직경 3.5 mm, 매식부 길이 10 mm인 Straumann 임플란트 몸체 외형에 서로 다른 4종의 나사산이 부여된 가상의 임플란트 모델 4개를 CAD 프로그램을 이용하여 각각 제작하였다. 4종 나사산은 buttress 형, v-자 형, reverse buttress 형, square 형이며, 나사산의 높이와 피치는 0.3 mm와 1.0 mm로 모두 동일하다. 각 임플란트가 3.8 mm pilot hole을 갖는, 1.2 mm 두께 치밀골에 식립되는 과정을 $DEFORM^{TM}$ 3D (ver. 6, SFTC, Columbus, OH, USA) 프로그램을 사용하여 모사/해석하였으며, 식립이 진행되는 과정에 인접골에 생성/누적되는 응력(식립응력)을 비교 분석하였다. 결과: 임플란트 식립 초기, 그 하단부가 pilot hole 내로 진입하며 나사산이 골벽을 압박/변형시키는 단계에서 식립 토오크와 응력이 급격히 발생하였으며 그 이후에 토오크와 응력이 모두 감소하는 변화를 보였다. 식립 응력은 임플란트 나사산 형상에 따라 현저한 차이가 있었으며, v-자형 나사산 경우가 가장 낮았고, square 형의 경우가 가장 높았다. 나사산 차이가 인접골 응력에 미치는 영향은 나사산 첨부 보다는 기저부에 인접한 위치에서 더 현저하였다. 결론: 임플란트 식립응력을 낮추어 골융합에 유리한 환경을 조성하는데는 나사산 첨부가 상대적으로 날카로운 v-자형 나사산이 유리하다.

• 소성∙가공
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• 제11권8호
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• pp.710-715
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• 2002

This paper describes the numerical determination of optimum blank diameter for sound material flow and high precise thread profile of a spindle screw through external thread rolling using two-three roll dies. Initial blank diameter affects the dimensional accuracy and surface finish qualities of a spindle screw in thread rolling process, therefore it is very important to determine the optimum blank diameter in thread rolling process. In order to determine the optimum blank diameter, this paper suggests the calculation method of initial bland diameter considering the real shape of tooth. The finite element code DEFORM is applied to analyze the metal flow of tooth, and these analytical results are verified by thread rolling experiment for spindle screw.

• 한국정밀공학회지
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• 제32권6호
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• pp.503-507
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• 2015

In this study, we compare the performance of the screw through the Clamping force of the test materials to change shape and structure, one of the ways to maintain and improve the engaging force to cope with the miniaturization of the fastener threads are further thinner and lighter precision way that can improve the fastening force of the screw results were as follows. The clamping force according to the materials was $7.57N{\cdot}cm$ in SUS XM7 and SWCH18A was $5.97N{\cdot}cm$. This result was to be found to average 13.5% high in the Clamping force of SUS XM7 materials. In the case of the clamping force of the screw thread shape change, the clamping force of symmetrical and asymmetrical thread was $6.78N{\cdot}cm$ and $7.57N{\cdot}cm$. The clamping force of the asymmetrical thread showed an average high of 11.6%.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.133-137
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• 2002

This paper summarizes the results of a numerical study conducted to analyze the determination of optimum blank diameter on material flow and thread profile for Spindle Screw in external thread rolling. Initial blank diameter affect a quality of Spindle Screw in thread rolling process. Therefore, it is very important to determine the optimum blank diameter in thread rolling process. In order to determine the optimum blank diameter, this paper suggest the calculating method of initial blank diameter considering real shape of tooth. The finite element code DEFORM is applied to analyze the metal flow of tooth. then the analytical results are verified by experiment of thread rolling for Spindle Screw.

• 한국기계가공학회지
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• 제16권3호
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• pp.38-44
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• 2017

The technology of electrical discharge tap machining may be appropriate for making thread out of highly brittle material. Especially, it is very difficult to machine tap with the traditional method if the brittle material has been hardened by quenching. In this study, the shape of electrical discharge blind hole tap machining was analyzed by discharge time, discharge current, and the flushing hole condition after quenched the tool steel of STD11 has discharged the tap shape with a screw-shaped copper(Cu) electrode. An experimental design was planned and analyzed by Taguchi robust experimental design. The result showed that the shape of the blind hole discharge tap was influenced by the flushing hole, discharge time, and discharge current. The most important factor of the processing conditions was found to be the discharge current. When blind hole EDM with a copper electrode with a flushing hole was conducted, the discharged shape was found to be smooth and the angle of the discharged tapped thread was also found to be close to the thread angle of $60^{\circ}$. As the values of discharge time and discharge current increased, the EDMed surface coarsened due to the increase of the single discharge energy and the shape of the thread collapsing.